Observation instruments, including optical instruments such as endoscopes, borescopes, and exoscopes may include an electronic imaging device located, for example, at the distal end of an elongated shaft or in a camera head which is connected to an elongated shaft. Whether positioned at the distal end of the endoscope shaft or in the camera head, the electronic imaging device may be one or more charge coupled devices (CCDs) or CMOS imaging devices together with other electronic components. Other electronic devices such as LED or other light sources may be included in the instrument. The camera head (or an instrument body or handle in the case of some observation instruments) is typically connected via a suitable cable to a camera control unit, commonly referred to as a “CCU.” The cable provides paths for carrying electrical power to the camera head and data signals to and from the camera head. In particular, image data captured by the imaging device is transmitted over the cable to the CCU for processing and ultimately for display on monitors which are connected directly to the CCU or to an intermediate monitor driving device. Control signals and power for operating the electronic components in the instrument may be transmitted over the cable from the CCU to the scope and/or camera head.
It is known in the art to transmit data signals from an endoscope to a CCU in the form of optical signals rather than electrical signals. U.S. Patent Application Publication 2015/0250378, for example, uses a cable between a camera head and CCU which includes optical fibers for carrying optical data signals from the camera head to the CCU. The camera head in this example includes circuitry for converting the captured image data from the electronic data signals generated by the imaging device to optical data signals which are then inserted into the optical fibers of the cable. U.S. Patent Application Publication 2015/0250378 also discloses that the cable from the camera head to CCU may include electrical signal paths in addition to the optical signal paths.
U.S. Patent Application Publication 2008/0225134 shows another endoscopic system having a cable between the CCU and camera head which includes both electrical signal paths and an optical path. In this case, the optical path is used to provide illumination light to the endoscope.
Medical devices such as endoscopes require an electrical isolation barrier between the CCU and camera head/endoscope. This electrical isolation barrier is required to ensure that an inappropriate electrical signal is not inadvertently applied to the endoscope and thus to the patient in which the endoscope is used. Where a cable running between the CCU and endoscope includes electrical signal paths, such as in both of the above-mentioned U.S. patent application publications, it has been necessary for the electrical isolation barrier to be included in the circuitry of the CCU. This requirement of the electrical isolation barrier in the CCU greatly complicates the circuitry of the device.